Process and adsorbent for separating ethanol and associated oxygenates from a biofermentation system

Abstract

Disclosed is a process and an adsorbent for the separation of ethanol associated oxygenates from a dilute mixture of ethanol and associated oxygenates in water in the presence of organic compounds derived from a biofermentation process. After pretreatment, the separation is carried out in a simulated moving bed adsorption system employing an stationary phase adsorbent comprising fluorinated carbon or modified C18 silica gel selective for the adsorption of ethanol and associated oxygenates, such as 2,3-butanediol, with a mobile phase desorbent selected from the group consisting of methanol, ethanol, propanol, and methyl tertiary butyl ether. The process is useful for removing water from dilute aqueous mixtures of organic compounds comprising ethanol in dilute concentration in water and produced by fermentation, biomass extraction, biocatalytic and enzymatic processes which are not economically recoverable by conventional distillation methods.

We claim: 
     
       1. A continuous SMB process for the recovery of ethanol from a biomass effluent stream from a fermentor, said biomass effluent stream comprising water, ethanol, at least one associated oxygenate, acetic acid, and suspended solids, wherein said SMB process having a desorption zone, a rectification zone, an adsorption zone, and a regeneration zone as SMB zones, wherein each SMB zone has an upper portion and a bottom portion and wherein the desorption zone, the rectification zone, the adsorption zone and the regeneration zone, each comprise one or more serially-linked adsorbent beds and each adsorbent bed containing a stationary phase adsorbent selective for the adsorption of ethanol and said associated oxygenate, said SMB process comprising:
 a. passing the biomass effluent stream to a pretreatment zone comprising a denaturation zone and a filtration zone and in the denaturation zone denaturating the biomass effluent stream to provide a denaturated biomass effluent stream and in the filtration zone filtering the denaturated biomass effluent stream through a filter having a filter size of less than or equal to 5 microns and adjusting pH to between about 5 and about 10 to provide a treated biomass effluent stream comprising water, at least one associated oxygenate, acetic acid and soluble biomass; 
 b. introducing the treated biomass effluent stream having a concentration of ethanol and the associated oxygenate being less than about 15 wt-% in water to the upper portion of the adsorption zone and withdrawing a raffinate stream comprising water and a minor portion of ethanol from the bottom portion of the adsorption zone; 
 c. passing a desorbent stream in a desorbent flow direction to the upper portion of the desorption zone and withdrawing a desorbent zone effluent stream from the bottom of the desorption zone and recovering a portion of the desorption effluent stream as an extract stream comprising ethanol, said associated oxygenate, acetic acid and a minor portion of water; 
 d. passing a remaining portion of the desorption effluent stream to the upper portion of the rectification zone and withdrawing a rectification zone effluent; 
 e. combining the rectification zone effluent with the treated biomass effluent stream prior to introducing the treated biomass effluent stream to the upper portion of the adsorption zone; 
 f. isolating a regeneration zone and passing a hot regeneration stream at a regeneration temperature to the upper portion of the regeneration zone and withdrawing a spent regeneration stream from the bottom portion of the regeneration zone and cooling the spent regeneration stream to provide a cooled spent regeneration stream; 
 g. passing the extract stream to a recovery zone to provide an ethanol product stream and an associated oxygenate product stream; and, 
 h. indexing the adsorbent beds sequentially in a direction which is counter current to the desorbent flow direction. 
 
     
     
       2. The process of  claim 1 , wherein the stationary phase adsorbent is selected from the group consisting of fluorinated carbon and modified C18 silica gel. 
     
     
       3. The process of  claim 1 , wherein the desorbent is selected from the group consisting of methanol, ethanol, propanol, and methyl tertiary butyl ether. 
     
     
       4. The process of  claim 1 , wherein the desorbent is ethanol. 
     
     
       5. The process of  claim 1 , wherein the hot regeneration temperature ranges from about 80° C. to about 120° C. 
     
     
       6. The process of  claim 1 , wherein the regeneration stream is selected from the group consisting of a gas stream, steam, water, and ethanol. 
     
     
       7. The process of  claim 1 , wherein the regeneration stream is a vent gas or combustion gas comprising methane, nitrogen, carbon oxides and hydrogen. 
     
     
       8. The process of  claim 1 , wherein the at least one associated oxygenate is selected from the group consisting of isopropyl alcohol (IPA), butanol (BuOH), n-butanol, t-butanol, hydroxymethyl-tetrahydrofuran or tetrahydro-2-furfuryl alcohol (THFA), 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,8-octanediol, etohexadiol, p-menthane-3,8-diol, 2-methyl-2,4-pentanediol, propanal, butanal, 2,5-furan-diacrboxyaldehyde, acetic acid, oxopropanoic acid, acrylic acid, levulinic acid, succinic acid, 2,5-furan-dicarboxylic acid, aspartic acid, glucaric acid, glutamic acid, itaconic acid, acetylacrylic acid, 4-O-Me-glucuronic acid, gluconic acid, and xylonic acid. 
     
     
       9. The process of  claim 1 , wherein the at least one associated oxygenate is 2,3-butanediol. 
     
     
       10. The process of  claim 1 , wherein the desorbent is ethanol and further comprising combining the cooled spent regeneration stream with the treated biomass effluent stream prior to introducing the treated biomass effluent stream to the upper portion of the adsorption zone. 
     
     
       11. The process of  claim 1 , further comprising reducing or removing acetic acid from the treated biomass effluent stream prior to step (a). 
     
     
       12. The process of  claim 9 , further comprising passing the raffinate stream to an ethanol water separation column to provide a recycle ethanol stream and heating and returning the recycle ethanol stream to the regeneration zone as the hot regeneration stream. 
     
     
       13. The process of  claim 1 , wherein the minor portion of water in the extract stream is less than 5 vol-%. 
     
     
       14. The process of  claim 1 , wherein the minor portion of ethanol in the raffinate stream is less than 5 vol-%. 
     
     
       15. The process of  claim 1 , further comprising passing the ethanol product stream to an ethanol dryer to provide a fuel grade ethanol stream. 
     
     
       16. A process for the recovery of ethanol from a biomass effluent stream comprising water, ethanol, 2,3-butanediol, acetic acid and soluble biomass, said process comprising:
 a. passing the biomass effluent stream to a pretreatment zone comprising a denaturation zone and a filtration zone and in the denaturation zone denaturating the biomass effluent stream to provide a denaturated biomass effluent stream and in the filtration zone filtering the denaturated biomass effluent stream through a filter having a filter size of less than or equal to 5 microns and adjusting pH to between about 5 and about 10 to provide a treated biomass effluent stream comprising water, at least one associated oxygenate, acetic acid and soluble biomass; 
 b. passing the treated biomass effluent stream having a concentration of ethanol and 2,3-butanediol being between about 6 wt-% and less than about 15 wt-% in water to a simulated moving bed adsorption zone having a plurality of adsorbent beds containing a stationary phase adsorbent selected from the group consisting of a fluorinated carbon adsorbent and a modified C18 silica gel, and a mobile phase desorbent selected from the group consisting of methanol, ethanol, and methyl tertiary-butyl ether (MTBE), wherein at least one adsorbent bed is regenerated at effective regeneration conditions with a regeneration stream selected from the group consisting of methanol, ethanol, hot water, steam, a vent gas stream, and combinations thereof to provide a raffinate stream comprising the mobile phase desorbent and water and an extract stream comprising ethanol, 2,3-butanediol, and dissolved solids, said extract stream being essentially free water; 
 c. passing the raffinate stream to a stripping zone to strip at least a portion of the desorbent from the water to provide a recovered desorbent stream and a waste water stream, and returning at least a portion of the recovered desorbent stream to the SMB zone as the desorbent stream; and, 
 d. passing the extract stream to a recovery zone to provide an ethanol stream and a butanediol stream. 
 
     
     
       17. The process of  claim 16 , wherein the filtered feed stream has a concentration of ethanol and 2,3-butanediol being between about 6 wt-% in water. 
     
     
       18. The process of  claim 16 , wherein the extract stream being essentially free of water has a water concentration equal to or less than about 5 vol-%. 
     
     
       19. The process of  claim 16 , wherein the stationary phase adsorbent is a fluorinated carbon adsorbent. 
     
     
       20. The process of  claim 19 , wherein the fluorinated carbon adsorbent is a surface modified carbon adsorbent comprising from about 0.5 to about 5 weight percent fluoride. 
     
     
       21. The process of  claim 19 , wherein the fluorinated carbon adsorbent is a surface modified carbon adsorbent comprising from about 1.5 to about 5 weight percent fluoride. 
     
     
       22. The process of  claim 16 , wherein the stationary phase adsorbent is a modified C18 silica gel. 
     
     
       23. The process of  claim 16 , wherein the mobile phase desorbent is methanol. 
     
     
       24. The process of  claim 16 , wherein the mobile phase desorbent is ethanol. 
     
     
       25. The process of  claim 16 , wherein the mobile phase desorbent is MTBE. 
     
     
       26. The process of  claim 16 , wherein the raffinate stream is essentially free of ethanol and 2,3-butanediol. 
     
     
       27. The process of  claim 24 , wherein the raffinate stream being essentially free of ethanol and 2,3-butanediol, said raffinate stream having a combined concentration of ethanol and butanediol equal to or less than about 5 vol-%. 
     
     
       28. The process of  claim 1 , wherein the feed stream comprises less than 2 wt-% of 2,3-butanediol. 
     
     
       29. The process of  claim 16 , wherein the regeneration section comprises a first regeneration section being regenerated with steam having a steam temperature of from about 100° C. to about 120° C. to provide a spent steam stream, condensing the spent steam stream to form a condensate stream at a condensate temperature of from 20° C. to 40° C., and combining the condensate stream with the filtered feed stream prior to passing the filtered feed stream to the SMB zone. 
     
     
       30. The process of  claim 16 , wherein the SMB zone comprises 10 adsorption beds, the desorption section comprising 2 adsorbent beds, the rectification section comprising 3 adsorbent beds, the adsorption section comprising 3 adsorbent beds, and the regeneration section comprising 2 adsorbent beds. 
     
     
       31. The process of  claim 16 , further comprising returning a portion of the ethanol stream to the SMB zone as the regeneration stream. 
     
     
       32. The process of  claim 16 , wherein the mobile phase desorbent comprises ethanol and at least a portion of the ethanol stream of step (f) is stripped to provide a stripped ethanol stream and the stripped ethanol stream is returned to the SMB zone as the mobile phase desorbent. 
     
     
       33. The process of  claim 16 , wherein the recovery zone of step (f) the extract stream is passed to an ethanol separator to provide the ethanol stream and an ethanol separator bottoms comprising butanediol and acetic acid and soluble biomass, passing the separator bottoms to an acetic acid recovery column to provide an acetic acid stream and a bottoms stream comprising butanediol and soluble biomass, and passing the bottoms stream to a butanediol column to provide the butanediol stream and a soluble biomass stream. 
     
     
       34. The process of  claim 32 , wherein the feed stream is an effluent stream from a biomass fermentation process and the mobile phase desorbent comprises ethanol wherein the raffinate comprising ethanol and water is passed to an azeotrope separation column to provide an ethanol stream and a waste water stream, passing the ethanol stream to an ethanol dryer to provide a fuel grade ethanol product. 
     
     
       35. The process of  claim 1 , wherein the biomass effluent stream is derived from the fermentation of corn, sugarcane, molasses, glucose, xylose, arabinose, and gases.